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Characterization and staging of rectal tumors: endoscopic ultrasound versus MRI / CT. Pictorial essay.

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Pictorial essay

DOI: 10.11152/mu.2013.2066.172.mri

Abstract

Endoscopic ultrasound is recommended for rectal cancer staging. Transrectal ultrasound approach is able to overcome one of the limitations of this technique regarding circumferential rectal stenosis. Prior intrarectal administration of a small amount of fluid contrast agent optimizes the method, making it easier to distinguish the layers of the rectal wall and tumor formation. Endoscopic ultrasound focuses on the gray-scale mode. Additional procedures provide useful information for tu- mor assessment: Doppler ultrasound helps identify chaotic intratumoral vascularization; 3D ultrasound allows the assessment and accurate measurement of the tumor; elastography can identify focal tumor dysplasia within adenomas; contrast-enhanced ultrasound allows characterization of tumor microvasculature. Even if they are not as accurate in distinguishing rectal wall lay- ers, cross-sectional imaging techniques (CT, MRI) can identify the anatomical relationships of advanced locoregional cancers, as well as possible distant metastasis. This paper aims at illustrating the main pathological aspects of endoscopic ultrasound multimodal examination useful for cancer staging.

Keywords: endoscopic ultrasound, CEUS, color elastography, rectal tumors

Characterization and staging of rectal tumors: endoscopic ultrasound versus MRI / CT. Pictorial essay.

Radu Badea

1

, Mariana M. Gersak

2

, Sorin M. Dudea

2

, Florin Graur

3

, Nadim Al Hajjar

3

, Luminița Furcea

3

1Ultrasound Imaging Laboratory, Department of Imaging and Radiology, “Octavian Fodor” Regional Institute of Gastroenterology and Hepatology, “Iuliu Hatieganu” University of Medicine and Pharmacy 2Department of Radiol- ogy Cluj County Clinical Emergency Hospital, “Iuliu Hatieganu” University of Medicine and Pharmacy, 33rd Surgical Clinic, “Octavian Fodor” Regional Institute of Gastroenterology and Hepatology Cluj-Napoca, Romania

Received 28.04.2015 Accepted 10.05.2015 Med Ultrason

2015, Vol. 17, No 2, 241-247

Corresponding author: Mariana M. Gersak Radiology Clinic

Cluj County Emergency Clinical Hospital 3-5 Clinicilor Street

400006, Cluj-Napoca, Romania E-mail: [email protected]

Introduction

The diagnosis, treatment and follow-up of patients with colorectal cancer has considerably improved in the recent years. Given the tendency to choose the optimal and at the same time least invasive treatment, the role of imaging methods have gained in importance for the diag- nosis, staging, and follow-up of patients with colorectal cancer. Thorough rectal cancer assessment and staging includes the local examination of the tumor (indicating the extent of rectal wall and neighboring tissues invasion

and the assessment of adjacent lymph nodes [1], the iden- tification of any distant metastases and synchronous in- testinal tumors [2]. There are several imaging techniques that can be used for rectal cancer assessment: endoscopic ultrasound, which is the most accessible and with good results for cancer staging; computed tomography (CT) and magnetic resonance imaging (MRI) are cross-sec- tional investigations that scan the entire body, identify- ing possible distant metastases or synchronous tumors.

Among these, endoscopic ultrasound has proven to be the best imaging technique in rectal tumors. A complete en- doscopic ultrasound multimodal examination may even surpass biopsy in terms of rectal cancer detection [3,4]

Ultrasound techniques

2D and 3D gray scale ultrasound. Endorectal and endovaginal US, in one term endoscopic US, represent the essential test for the local assessment of rectal tu-

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mors. It is easy to perform and well-tolerated, requiring minimal prior preparation (enema), providing essential morphological information for cancer diagnosis and staging (uTNM). When performed after administration of small quantities of water (100-150 cc), the method can be a very useful diagnostic tool (fig 1). Transrectal (TR) US is useful for the assessment of tumor morphol- ogy and tumor size, tumor extension into the longitudi- nal rectal muscle and inside it, tumor location in relation to the anus, and perirectal lymph node characterization [5,6]. All these aspects are summarized in Table I [7].

3D US allows accurate measurement of rectal tumors and identification of anatomical relationships, which assists the surgical planning procedure. Processing the data ac- quired by 3D US makes possible the visualization of rec- tal tumors in a way similar to digestive endoscopy (fig 2).

Elastography. It is an ultrasound application that has already proved useful in various clinical fields [8]. So far,

the association between TRUS and elastography proved particularly useful in assessing prostate, rectal tumors being less studied. Of all types of elastography (ARFI, SWE and color/strain elastography), rectal cancer as- sessment was mainly based on strain/color elastography (SE), probably because this type of elastography is com- monly present with ultrasound equipment (fig 3).

Doppler ultrasound. This technique is useful for the assessment of rectal tumors, providing information about the characteristics of the blood vessels located in the in- tra- and peritumoral areas. Color flow mapping (CFM) identifies the presence of blood vessels and the direction of the blood flow, while the spectral method provides in- formation on the characteristics, direction and the type of blood flow.

Contrast-enhanced ultrasound (CEUS). This appli- cation of TRUS has not yet been fully explored in relation to rectal tumors, but there are many studies in other areas Table I. Rectal cancer staging [7].

Tprimary tumor Tx – primary tumor cannot be assessed T0 – no evidence of primary tumor

Tis – carcinoma in situ: intraepithelial tumor or invasion of lamina propria T1 – tumor invades submucosa

T2 – tumor invades muscularis propria

T3 – tumor invades through the muscularis propria into pericolorectal tissues T4a – tumor penetrates to the surface of the visceral peritoneum

T4b – tumor directly invades or is adherent to other organs or structures.

Nregional lymph nodes Nx – regional lymph nodes cannot be assessed N0 – no regional lymph node metastasis N1 – metastases in 1–3 regional lymph nodes N1a – metastasis in 1 regional lymph node N1b – Metastases in 2–3 regional lymph nodes

N1c – tumor deposit(s) in the subserosa, mesentery or nonperitonealized pericolic, or perirectal tissues without regional nodal metastasis

N2 – metastases in ≥4 regional lymph nodes N2a – metastases in 4–6 regional lymph nodes N2b – Metastases in ≥7 regional lymph nodes Mdistant metastasis M0 – no distant metastasis

M1 – distant metastasis

M1a – metastasis confined to 1 organ or site (e.g. liver, lung, ovary, non-regional node).

M1b – metastases in >1 organ/site or the peritoneum

Fig 1. Transvaginal ultrasound with rectal re- laxation using water enema. Stage T2 villous tumor (arrow).

Fig 2. Transrectal ultrasound – three-dimen- sional reconstruction of villous adenoma.

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of interest, where it has demonstrated its importance in the characterization of tumoral lesions. Immediately after the injection of the contrast medium, the microbubbles reach the rectum, especially the areas where microcir- culation is more abundant. The images must be stored for further analysis of loading and unloading curves and for a more objective interpretation, according to the time intervals acquired on these curves. In order to calculate these curves and easily identify the differences between them, one or more ROIs must be manually selected on the equipment, one for the tumor-bearing region and an- other for an apparently tumor-free region. The most im- portant time-intensity parameters that can be acquired on the loading and unloading curves are the following: con- trast arrival time in the ROI (AT), maximum contrast me- dium enhancement (time to peak – TTP), maximum con- trast intensity (peak intesity – PI), area under the curve (AUC), loading time (WIT), ascending slope (AS) and echo intensity (EI) [9-11]. With the help of these parame- ters, CEUS offers very good interobserver variability [9].

Cross-sectional imaging techniques

CT. It is a radiating technique, but it has the advan- tage of rapid acquisition scans. Preparation prior to CT scan includes water enemas. Portal-phase CT scan was proposed in order to reduce the degree of radiation, with similar results obtained for arterial and venous phases [12]. CT with intravenous administration of iodine based contrast medium shows limited soft tissue contrast for local staging of early tumors [2,5]. CT scan cannot distin- guish between the layers of the rectal wall [13]. However, multidetector CT (MDCT) with multiplanar reconstruc- tion (MPR) has a good accuracy for the assessment of lo- coregionally advanced tumors (T3, T4) (87.1% for tumor assessment and 84.8% for lymph node assessment) [13].

MRI. It is a non-radiating cross-sectional imaging technique, but the acquisition of all sequences takes long- er than in the case of a CT scan. However, MRI has be-

come increasingly popular for rectal cancer diagnosis and staging. Compared to CT, MRI shows better soft tissue contrast and, in addition, it has many advantages: it em- phasizes tumor relationships with the rectum, mesorec- tal fascia, and adjacent tissues, it identifies pelvic lymph nodes and possible vascular infiltration [2,14]. The use of the endorectal coil increases the diagnostic value of the method in the evaluation of rectal tumors. The basic MRI protocol includes either the T2 sequence alone, or the ad- ditional T1 sequence. Using fat-suppressed T2 sequences is useful to emphasize perirectal fat invasion [15]. The administration of Gadolinium based contrast agents does not bring additional information for the diagnostic accuracy of magnetic resonance imaging. Of all MRI sequences, the T2 sequence is the most appropriate to identify rectal wall layers. This sequence is characterized by hyperintense mucosa and submucosa, which makes it difficult to distinguish one from the other; relatively hy- pointense muscularis propria; hyperintense layer repre- senting the perirectal fat tissue. The mesorectal fascia is a linear structure, smooth and hypointense, encompassing the mesorectum [15] (fig 4).

Endoscopic US assessment of rectal cancer. Rectal tumors present varied echogenicity, and in evolution de- termine disruption and upheaval of rectal layers. TRUS allows identification of tumor morphology, size and loca- Fig 3. Color elastography. Rigid tumor formation (*) as com-

pared to perirectal soft tissues (arrows).

Fig 4. MRI scan without contrast medium, coronal section. Normal stratification of the rectum: mucosa and submucosa (white arrow);

muscle (black arrow); perirectal tissue (*).

Fig 5. Hypoechoic rectal tumor, circumferen- tial, stage T3 (white arrows). Small peritumoral lymph node (black arrow).

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tion in relation to the anus, assessment of lymph node morphology and size, if present, and, of course, uTNM staging [5] (fig 5-7). 3D US shows similar or even higher accuracy than 2D US in the evaluation of rectal tumors (Acc=78-88% for 3D and 69-84% for 2D US) [16,17].

The 3D image can be impressive.

Pathological lymph nodes with ≥5-7mm in size are hypoechoic and round [5,18-20].

Rectal tumors have intense and chaotic vasculature (fig 8). The contribution of Doppler ultrasound to can- cer staging is not significant, but it is extremely useful to distinguish tumor recurrence from postoperative scar- ring [21]. Malignant lymph nodes have a RI≥0.61 and PSV≥20cm/second [20].

Elastography can distinguish malignant form benign tumors (malignant tumor mean strain ratio value over 1.25 and benign tumor mean strain ratio value below 1.25 [4]. In terms of cancer staging, elastography, along with TRUS, is useful to distinguish pT0 stage from pT1 stage, with better results than MRI, including pretreatment biopsy. Elastog- raphy, additional to TRUS, does not bring additional infor- mation regarding T2 and T3 staging, as TRUS is sufficient for final cancer staging [3] (fig 9). To our knowledge, the characterization of pathological lymph nodes did not in- clude their elasticity but, by our experience, these appear more rigid than perirectal fat during elastography (fig 10).

CEUS. The contrast agent is homogeneously re- tained by all rectal adenomas, and, compared to tumor- Fig 6. Power Doppler ultrasound. Rectal tumor

with intense and chaotic vascularization (stage T2).

Fig 7. Hypoechoic rectal tumor, circumferen- tial (Tu), which comes in contact with the pros- tate gland (*), stage T4.

Fig 8. Color Doppler ultrasound of a large hy- poechoic rectal tumor with intense vasculariza- tion and irregular vascular distribution.

Fig 9. Rigid lymph node for color elastography (arrow). Tu = tumor

Fig 10. a) Circumferential rectal tumor gray scale; CEUS: b) Rapid and intense uptake in the arterial phase (19 sec); c) Rapid contrast washout in the venous phase (46 sec).

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free rectal wall the contrast medium becomes visible later and with lower intensity. Difficulty may arise in case of larger adenomas with increased uptake. Adeno- carcinomas are irregular and, compared to the tumor-free rectal wall, the contrast medium loads faster and contrast maximum enhancement occurs earlier [10]. Specifically, aggressive tumors with high degree of angiogenesis have an increased inhomogeneous contrast uptake. An excep- tion to this rule is that of large tumors with intratumoral necrosis, which can have a low contrast uptake or even no uptake [10] (fig 11).

Limitations

There are relatively few limitations of endoscopic US;

difficulties may occur in the case of high rectal tumors,

where the transducer cannot penetrate, in the evaluation of circumferential neoplasms, stenotic in men, in case of posterior rectal curving, which may limit optimal visu- alization of tumors on the posterior wall of the rectum.

Since the introduction of the water enema procedure, the presence of air and feces in the rectum is no longer a significant drawback [22-24]. However, there is still the question whether the presence of water does not restrict the use of elastography, giving rise to artifacts. Also, the transvaginal approach can be used for stenotic tumors, circumferential in women, thus offering a much better visualization than the transrectal approach [22,25].

CT. Even if CT cannot differentiate rectal wall layers, rectal tumors can be identified using iodine-containing contrast medium, involving the perirectal fat tissue and adjacent organs (in more advanced stages). To assess T3- T4 tumor stages, CT with MPR showed good accuracy (87.1%) [13] (fig12, fig 13). CT scan is inferior to TRUS and MRI with endorectal coil when identifying peritu- moral lymph node metastasis [26].

MRI. Rectal lesions show increased signal intensity than the muscle layer and lower signal intensity than the submucosa [27]. Identification of tumor lymph nodes as- sessed using MRI strictly from a size perspective is not plausible [28]. To identify lymph node invasion using MRI, lymph node morphology must be taken into ac- count, such as the irregular contours and inhomogeneous intranodal signal intensity, rather than their size [28]. In Fig 11. Transvaginal ultrasound. Hypoechoic

circumferential rectal tumor, stage T3 (arrows).

Fig 12. CT scan- axial (a), coronal (b) and sagittal view (c), with iv. contrast medium. Circumferen- tial rectal tumor, with contrast uptake – stage T3 (arrows). Courtesy of Dr. Adrian Brumboiu.

Fig 13. CT scan – axial (a) and coronal (b) view, with iv. con- trast medium. Rectal tumor with contast uptake and perineal ex- tension – stage T4 (arrows). Courtesy of Dr. Adrian Brumboiu.

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evaluating perirectal lymph nodes, MRI was significantly improved by using the endorectal coil, obtaining the high- est accuracy of all imaging investigations [26] (fig 14-16).

The main limitation of CT is that it cannot identify the rectal layers individually and it shows a low soft tissue contrast, thus unable to identify early stage rectal can- cer. It should also be taken into account that this type of examination cannot be performed in people allergic to iodine. Regarding MRI, some of its drawbacks include the high costs, poor accessibility, the length of the proce- dure and general contraindications in patients with pace- makers, various metal prostheses and in those who suffer from claustrophobia.

Conclusions

Gray scale endoscopic US is a good choice for the local assessment of rectal tumors. Additionally, every TRUS application brings useful information in the diag- nosis, staging and reassessment of rectal tumors: Dop- pler US emphasizes intratumoral hypervascularization and differentiates between postsurgical scarring and lo- cal recurrences; 3D US measures the volume, the exact size of the tumor, identifying its spatial position and the relationships with adjacent tissues; elastography is useful for early rectal cancer staging and for the differentiation between malignant tumors and adenomas; CEUS identi- fies intratumoral microcirculation. All these applications have the great advantage of being accessible and appli- cable as part of the same examination, radiation-free and with good diagnostic accuracy. Endoscopic US cannot replace cross-sectional examinations that can scan the entire body of the patient, in search of possible distant metastasis, but when it comes to local examination, it is the method of choice for all rectal tumors.

Conflict of interest: none

References

1. Beets-Tan RG, Beets GL. Rectal Cancer: Review with Em- phasis on MR Imaging. Radiology 2004; 232: 335-346.

2. Tapan Ü, Özbayrak M, Tatli S. MRI in local staging of rec- tal cancer: an update. Diagn Interv Radiol 2014; 20: 390- 3. Waage JE, Leh S, Rosler C, et al. Endorectal ultrasonogra-398.

phy, strain elastography and MRI differentiation of rectal adenomas and adenocarcinomas. Colorectal Dis 2014 Nov 18. doi: 10.1111/codi.12845.

4. Waage JE, Havre RF, Odegaard S, Leh S, Eide GE, Baatrup G. Endorectal elastography in the evaluation of rectal tu- mours. Colorectal Dis 2011; 13: 1130-1137.

5. Akbari RP, Wong WD. Endorectal ultrasound and the pre- operative staging of rectal cancer Scand J Surg 2003; 92:

25-33.

6. Hildebrandt U, Feifel G. Preoperative staging of rectal can- cer by intrarectal ultrasound. Dis Colon Rectum 1985; 28:

42-46.

7. How is colorectal cancer staged? Available at: http://www.

cancer.org/cancer/colonandrectumcancer/detailedguide/

colorectal-cancer-staged. Accesed 2015 May 5.

8. Cosgrove D, Piscaglia F, Bamber J, et al. EFSUMB Guide- lines and recommendations on the clinical use of ultrasound elastography. Part 2: Clinical applications. Ultraschall Med 2013; 34: 238-253.

9. Zhuang H, Yang ZG, Wang ZQ, et al. Features of time- intensity curve parameters of colorectal adenocarcinomas Fig 14. MRI scan – bulging rectal tumor for-

mation, confined to the muscular layer – stage T2 (*)

Fig 15. MRI scan – rectal tumor formation, stage T3 (*) with perirectal fat tissue invasion (arrow).

Fig 16. MRI scan – circumferential rectal tu- mor formation, stage T4 (*), with seminal vesi- cle invasion (black arrow) and lymph nodes (white arrows).

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evaluated by double-contrast enhanced ultrasonography:

initial observation. Eur J Radiol 2012; 81: 677-682.

10. Lu M, Yan B, Song J, Ping W, Yue LX, Song B. Double- contrast-enhanced sonography for diagnosis of rectal le- sions with pathologic correlation. J Ultrasound Med 2014;

33: 575-583.

11. Wang Y, Li L, Wang YX, et al. Time-intensity curve pa- rameters in rectal cancer measured using endorectal ultra- sonography with sterile coupling gels filling the rectum:

correlations with tumor angiogenesis and clinicopathologi- cal features. Biomed Res Int 2014; 2014: 587806.

12. Mainenti PP, Cirillo LC, Camera L, et al. Accuracy of sin- gle phase contrast enhanced multidetector CT colonogra- phy in the preoperative staging of colo-rectal cancer. Eur J Radiol 2006; 60: 453-459.

13. Sinha R, Verma R, Rajesh A, Richards CJ. Diagnostic value of multidetector row CT in rectal cancer staging: compari- son of multiplanar and axial images with histopathology.

Clin Radiol 2006; 61: 924-931.

14. Bipat S, Glas AS, Slors FJ, Zwinderman AH, Bossuyt PM, Stoker J. Rectal cancer: local staging and assessment of lymph node involvement with endoluminal US, CT, and MR imaging – a meta-analysis. Radiology 2004; 232: 773- 15. Iafrate F, Laghi A, Paolantonio P, et al. Preoperative staging 783.

of rectal cancer with MR Imaging: correlation with surgi- cal and histopathologic findings. Radiographics 2006; 26:

701-714.

16. Kim JC, Kim HC, Yu CS, et al. Efficacy of 3-dimensional endorectal ultrasonography compared with conventional ultrasonography and computed tomography in preoperative rectal cancer staging. Am J Surg 2006; 192: 89-97.

17. Hünerbein M, Pegios W, Rau B, Vogl TJ, Felix R, Schlag PM. Prospective comparison of endorectal ultrasound, three-dimensional endorectal ultrasound, and endorectal MRI in the preoperative evaluation of rectal tumors. Pre- liminary results. Surg Endosc 2000; 14: 1005-1009.

18. Glaser F, Layer G, Zuna I, van Kaick G, Schlag P, Herfarth C. Preoperative assessment of perirectal lymph nodes by ultrasound. Chirurg 1990; 61: 587-591.

19. Hildebrandt U, Feifel G. Importance of endoscopic ultra- sonography staging for treatment of rectal cancer. Gastroin- test Endosc Clin N Am 1995; 5: 843-849.

20. Heneghan JP, Salem RR, Lange RC, Taylor KJ, Hammers LW. Transrectal sonography in staging rectal carcinoma:

the role of gray-scale, color-flow, and Doppler imaging analysis. AJR Am J Roentgenol 1997; 169: 1247-1252.

21. Sudakoff GS, Gasparaitis A, Michelassi F, Hurst R, Hoff- mann K, Hackworth C. Endorectal color Doppler imaging of primary and recurrent rectal wall tumors: preliminary ex- perience. AJR Am J Roentgenol 1996; 166: 55-61.

22. Scialpi M, Zottele F, Niccolini M, Dalla Palma F. Transvagi- nal echography in the study of the rectum. A new method with rectal distension with water. Radiol Med 1993; 85: 203-208.

23. Scialpi M, Niccolini M, Zottele F, Dalla Palma F, Scialpi P.

A new method for study of the rectum using transvaginal ultrasound with water enema. Abdom Imaging 1996; 21:

342-344.

24. Scialpi M, Rotondo A, Angelelli G. Water enema transvagi- nal ultrasound for local staging of stenotic rectal carcinoma.

Abdom Imaging 1999; 24: 132-136.

25. Badea R, Badea G, Dejica D, Henegar E. The role of trans- vaginal sonography as compared with endorectal sonogra- phy in the evaluation of rectal cancer: preliminary study.

Surg Endosc 1991; 5: 89-91.

26. Kwok H, Bissett IP, Hill GL. Preoperative staging of rectal cancer. Int J Colorectal Dis 2000; 15: 9-20.

27. Brown G, Richards CJ, Newcombe RG, et al. Rectal carci- noma: thin-section MR imaging for staging in 28 patients.

Radiology 1999; 211: 215-222.

28. Brown G, Richards CJ, Bourne MW, et al. Morphologic predictors of lymph node status in rectal cancer with use of high-spatial-resolution MR imaging with histopathologic comparison. Radiology 2003; 227: 371-377.

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